Date picker: Dropdown should trigger with text input

Problem

Currently, we differentiate between two different interactions with our date picker component. You can either:

1. Enter the date with text
2. Select the date with a dropdown

Proposal

Create a more cohesive component feel by integrating both of these interactions together:

1. When text input field is clicked, open dropdown but keep text input field active
2. When dropdown is open and text input field is clicked, keep dropdown open and reflect text input in the calendar UI